Canal History- Navigational History

The southeast corner of New England, to which the name "Cape Cod" was given by the explorer, Bartholomew Gosnold in 1602, reaches out in the form of a narrow, hooked spit to one of the two most hazardous sections of the Atlantic Coast. It is said that experienced mariners fear the waters to the east and south of Cape Cod more than those off Cape Hatteras. The hazardous region off Cape Cod, known as Nantucket Shoals, and consisting of a bottom of shifting sand over which the depth varies from 1 to 25 fathoms, extends about 70 miles almost due south from the southernmost part of Cape Cod at Monomoy Point to the navigational aid which replaced the "Nantucket Light Ship", marking the outer limit of the area. In traversing the Cape Cod section of the coast, waterborne traffic had, until 1914 (when the Canal was opened to traffic), the choice between two routes; the all-sea route outside the Nantucket Light Ship, or the Vineyard Sound route, which entailed navigating a zigzag course through tortuous channels in the Nantucket Shoals area, passable only by a limited number of vessels. The larger vessels were forced to use the route around the Nantucket Light Ship.

Although these routes are lighted and well marked, the difficulties attending their navigation are increased by the prevalence in the area of dense fog caused by evaporation due to the meeting of warm, easterly air currents and cold currents from the Maine coast. The 300-year history of navigation in this section reflects the natural hazardous conditions of this area of shoals, irregular courses, currents, wind, ice and fog and a general lack of refuge, with a long, tragic list of wrecks and their accompanying toll of lives, cargoes, and ships.

Colonel Edward Durr, C.E., stated in 1922, "the special economic function of a Cape Cod Canal is to provide a route that will be economically more desirable to traffic than the natural routes around Cape Cod through the elimination of dangers and delays and the expense resulting there from."

In spite of the increase in Canal traffic after its purchase by the Government in 1928, the use of this waterway was limited by its narrow width and shallow depth to the smaller type of vessel. Large vessels were still forced to use the outside route. In the 15-year period prior to 1930, 75 accidents occurred in the Canal, causing an estimated loss of $800,000. The cause of most of these accidents can be traced to the narrow channel then existing, to rapid currents, or to their combined adverse influence.

The special economic function of the Canal was not completely fulfilled by its original construction or by its ownership and operation by the Government. Because of the limited dimensions, the many benefits accruing from the use of the Canal were not available to all classes of shipping. Therefore, as a result of numerous economic studies, physical surveys and hydraulic investigations, improvement was undertaken with a view to serving adequately that large and very important part of the nation's waterborne commerce.

The Canal has what can be a confusing range of tides. Mean tide range in Cape Cod Bay is 9.4 ft. but only 4 ft. in Buzzards Bay. The phase and mean tide levels also differ in the two bays. This differential produces high tide in Buzzards Bay three hours ahead of that in Cape Cod Bay. Mean tide is five feet higher in the latter bay. The currents reverse direction every six hours, and a maximum current velocity of 5.2 knots is generated. The effect of these tidal phenomena on a theoretical Canal section of 540 feet wide and 32 feet deep has been studied with the aid of a model 115 feet in length and constructed at the Massachusetts Institute of Technology.

This model yielded valuable data which were useful in planning the present Canal. It was built of concrete to a horizontal scale of 1:600 and a vertical scale of 1:60. Tides were automatically created by an electrical water-level control mechanism, and water levels at stations along the model were obtained by an electrical water-level indicator. Both devices gave results to 1/100 inch in the model. In addition to the determination of hydraulic data, the study disclosed serious eddy and crosscurrent conditions in Buzzards Bay, which were corrected by the construction of dikes. These dikes were constructed by the disposal of the material dredged hydraulically from the Buzzards Bay approach channel. Hog Island, or Buzzards Bay Channel, the straight western approach to the Canal with a width of 500 feet and a depth of 32 feet at mean low water, was opened to navigation on April 22, 1937. The mooring basins at the easterly and westerly ends of the Canal are equipped with mooring dolphins, the depth available at the former is 25 feet, and at the latter, 32 feet, both at mean low water.

The land through which the Canal passes is composed principally of sand, although gravel, cobbles, and boulders are present. Much of the sand is fine and capable of being moved by tidal currents and the surface waves caused by wind or the passage of vessels. To preserve and protect the bank slope and alignment of the sides of the Canal from this wave wash, revetment 2 feet thick, composed of riprap and crushed stone, and extending 5 feet below water level to 5 feet above high water, has been placed on both banks for the whole length of the Canal. The revetment work was done largely in the dry, prior to widening the Canal by dredging.

The project depth of 32 feet at mean low water was selected because it will accommodate nearly all vessels entering or leaving the ports of Boston and Portland. The increase in Canal traffic is reflected not only in the number of vessels using the Canal, but also in the average size and value of the cargo.

The traffic in the Canal reflects the commercial and industrial activity of New England. Savings of distance, fuel and time, more reliable ship schedules, and other incidental benefits are available to practically all coastwise and intercoastal shipping serving this important section of the nation's industrial and economic life.